Low thread force cable tie with anchored locking device

ABSTRACT

A two piece cable tie is provided having an improved metal locking device anchoring system. The cable tie includes a strap including a first end and a free end and a locking head secured to the first end of the strap that defines a strap accepting channel in the head having a strap entry end and a strap exit end. The locking head further includes a metal locking device receiving cavity adjacent to and open toward the strap exit end of the locking head and a mounting slot having an inner support wall, an outer support wall and a support slot communicating the mounting slot with the receiving cavity. A metal locking device is mounted through the metal locking device receiving cavity into the mounting slot. The metal locking device has a free end positioned within the strap accepting channel and a fixed end having at least one bent tang protruding outwardly from a surface of the metal locking device. The fixed end having the at least one bent tang is insertable through the support slot. Upon such insertion, the inner support surface of the mounting slot resiliently urges at least a protruding edge of the at least one bent tang against the outer support surface to anchor the metal locking device within the mounting slot and resist withdrawal of the metal locking device in a direction towards the exit end of the strap accepting channel. The inventive cable tie is capable of multiple strap threading without failure. The barbed anchoring system and method are particularly suited for cable ties having a bent metal locking device with a mounting slot parallel with the strap accepting channel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 09/855,262,filed May 15, 2001, now U.S. Pat. No. 6,530,126.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to a low thread force two piececable tie. More particularly, the invention relates to a locking devicefor such a cable tie that has an integral protruding tang serving as ananchoring device.

2. Description of Related Art

Plastic cable ties having metal locking device inserts are well known inthe art. Examples of such include U.S. Pat. No. 3,457,598 to Mariani andU.S. Pat. No. 5,517,727 to Bernard et al.

Cable ties of this type include a metal locking device partiallyembedded at an angle within a strap accepting channel of a cable tiehead. The metal locking device is situated at an angle that allowsinsertion of a cable tie strap in an insertion direction, but allows forengagement of the locking device with the strap when it is pulled in aremoving direction to prevent removal. The metal locking device of suchcable ties is in the form of a cantilevered beam that is fixed at oneend and extends into the strap accepting channel at the free end.Operation of such a cable tie will be described with respect to FIGS.1-3, which show operation of a cable tie device according to copendingU.S. patent application Ser. No. 09/855,383, the subject matter of whichis incorporated herein by reference in its entirety.

The cable tie 100 of FIG. 1 includes a strap 104 (partially shown)integral with a cable tie head 102. Cable tie head 102 is formed with alocking device receiving cavity 180 and a strap accepting channel 122having a strap entrance 168 and a strap exit 166. Strap acceptingchannel 122 receives the leading end 112 of strap 104. Locking devicereceiving cavity 180 receives a pre-formed metal locking device 136,which is formed from a corrosion resistant metal such as stainlesssteel.

Locking device receiving cavity 180 is provided to allow access to theanchoring region on the end wall for partial embedding of metal lockingdevice 136 in a mounting slot 130 of the cable tie head 102. Mountingslot 130 may be preformed in an interior surface of cavity 180 or may bepartially formed as a result of pressing an end 134 of locking device136 into the interior surface of cable head 102. This defines acantilever beam structure having a fixed end 134 and a free end 138 thatextends into strap accepting cavity 122. Metal locking device receivingcavity 180 also allows for movement of locking device 136.

As shown in FIG. 1, upon insertion of strap end 112 into the strapaccepting channel, the free end of metal locking device 136 freelyflexes due to the resiliency of the metal and the angle of the device toprovide a low insertion force. Insertion of the cable tie strapcontinues to occur until strap 104 is sufficiently tight around anobject to be constrained, such as an unshown cable bundle. Upon releaseof the strap, or through application of a withdrawal force on the strap,forces flex free end 138 of metal locking device 136 and cause asharpened portion of free end 138 to begin to pierce strap 104 as shownin FIG. 2. When free end 138 sufficiently rests upon the fulcrum point142, resistance to further withdrawal is attained up to a determinabletensile strength value, which is dependent on material selection andother variables.

Such a cable tie is sufficient for a single locking application (i.e., asingle tightening operation). However, what occasionally happens is thatafter an initial tightening or attempt to withdraw the cable tie strap104, a subsequent tightening or re-threading action may be initiated tofurther cinch down the cable tie. As the free end 138 of metal lockingdevice 136 has already partially penetrated the surface of strap 104, itis possible that during these further re-thread attempts to advance thestrap in the direction of exit 166, the free end will not break freefrom strap 104. Instead, the locking device 136 will remain partiallyembedded within the surface of strap 104. In such cases, if theretention force of the fixed end 134 is less than the withdrawal forcenecessary to break away free end 138 from strap 104, it is possible thatfixed end 134 will be pulled out of slot 130. This is undesirable andresults in cable tie failure as shown in FIG. 3, in which metal lockingdevice 136 is either completely removed or sufficiently withdrawn fromslot 130 to adversely affect proper cable tie functioning. In thisexample, the retention force acting on fixed end 134 to resist removalis the frictional force between fixed end 134 and slot 130. Thisretention force may be insufficient and is particularly problematicwhere the fixed end is oriented substantially parallel to there-threading force acting on strap 104 toward exit 166, as in thisexample.

There is a need for a two-piece cable tie having an improved anchorretention system for a metal locking device.

There also is a need for a method of easily forming a barbed tang on ametal locking device of a cable tie to serve as an anchor.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a two-piece cable tie with alocking device that has improved anchoring force to resist removalduring initial and subsequent re-threading.

It also is an object of the invention to provide a method of forming abarbed tang on a metal locking device of a cable tie.

It is further an object of the invention to punch one or more tangs ontoa metal locking device so as to form a ramp that is in a directionconducive to installation but provides resistance to attempts towithdraw the device.

The above and other objects are achieved by a cable tie having ananchored metal locking device, comprising: a strap including a first endand a free end; a locking head secured to the first end of the strap,the locking head defining a strap accepting channel in the head having astrap entry end and a strap exit end, the locking head further includinga metal locking device receiving cavity adjacent to and open toward thestrap exit end of the locking head, the locking head further including amounting slot having an inner support wall, an outer support wall and asupport slot communicating the mounting slot with the receiving cavity;and a metal locking device mounted through the metal locking devicereceiving cavity into the support cavity, the metal locking devicehaving a free end positioned within the strap accepting channel and afixed end having at least one bent tang protruding outwardly from asurface of the metal locking device. The fixed end having the at leastone bent tang is insertable through the support slot. Upon suchinsertion, the inner support surface of the mounting slot resilientlyurges at least a protruding edge of the at least one bent tang againstthe outer support surface to anchor the metal locking device within themounting slot and resist withdrawal of the metal locking device in adirection towards the exit end of the strap accepting channel.

The invention also provides a method of forming a cable tie having animproved anchoring system comprising the steps of: forming a cable tiehaving a strap including a first end and a free end and a locking headsecured to the first end of the strap, the locking head defining a strapaccepting channel in the head having a strap entry end and a strap exitend, the locking head further including a metal locking device receivingcavity adjacent to and open toward the strap exit end of the lockinghead, the locking head further including a mounting slot having an innersupport wall, an outer support wall and a support slot communicating themounting slot with the receiving cavity; forming a metal locking devicewith a fixed end having at least one bent tang and a free end; initiallymounting the metal locking device through the metal locking devicereceiving cavity into the mounting slot by inserting the fixed endthrough the support slot until the fixed end is urged against the innersupport wall; and further inserting the metal locking device into themounting slot and causing the inner support surface to be resilientlydeformed until the at least one bent tang is substantially receivedwithin the mounting slot, at which time the inner support surface urgesat least an edge of the at least one bent tang against the outer supportsurface to securely anchor the metal locking device to the mountingslot.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of thepresent invention will become apparent from the following description ofpreferred embodiments with reference to the accompanying drawings,wherein:

FIG. 1 is a cross-sectional view of an initial threading of a cable tiestrap according to a related invention;

FIG. 2 is a cross-sectional view of the cable tie of FIG. 1 showing thecable tie strap after a locking operation has been performed;

FIG. 3 is a cross-sectional view of the cable tie of FIG. 1 showing thecable tie strap after a re-threading operation;

FIG. 4 is a lower perspective view of a cable tie according to theinvention;

FIG. 5 is a bottom view of the cable tie of FIG. 4;

FIG. 6 is top partial view of a cable tie according to the invention;

FIG. 7 is a cross-sectional view of the cable tie of FIG. 6 taken alongline 7—7 according to a first embodiment showing a partially installedmetal locking device;

FIG. 8 is a blow-up partial view of FIG. 7;

FIG. 9 is a cross-sectional view of a fully installed metal lockingdevice according to the first embodiment;

FIG. 10 is a perspective view of a metal locking device according to afirst embodiment of the invention;

FIG. 11 is a top view of the metal locking device of FIG. 10;

FIG. 12 is another perspective view of the metal locking device of FIG.10;

FIG. 13 is a side view of the metal locking device of FIG. 10;

FIG. 14 is a top view of a second embodiment of the metal locking deviceaccording to the invention;

FIG. 15 is a side view of a metal locking device of FIG. 14;

FIG. 16 is a top partial view of a cable tie according to a secondembodiment of the invention;

FIG. 17 is a cross-sectional view of the cable tie of FIG. 16 takenalong line 17—17 showing a partially installed metal locking device;

FIG. 18 is a blow-up partial view of FIG. 17;

FIG. 19 is a cross-sectional view of the cable tie of FIG. 17 with afully installed metal locking device;

FIG. 20 is a blow-up partial view of FIG. 19;

FIG. 21 is a cross-sectional view of the cable tie of FIG. 19 takenalong line 21—21;

FIG. 22 is a bottom view of the cable tie according to the secondembodiment;

FIG. 23 is a partial perspective view of the cable tie of FIG. 22;

FIG. 24 is a perspective view of a die and punch used to make the metallocking device of FIGS. 10-13 before the punch has acted on the lockingdevice;

FIG. 25 is a top view of the punch of FIG. 24 engaged with the lockingdevice;

FIG. 26 is a front section of the punch of FIG. 24 engaged with thelocking device;

FIG. 27 is a right side section view of the punch of FIG. 24 engagedwith the locking device;

FIG. 28 is a perspective view of the punch and die of FIG. 24 after thepunch has acted on the locking device;

FIG. 29 is a close-up of the die of FIG. 28 showing formed bent tangs;

FIG. 30 is a perspective view of an alternative die and punch with anadditional support base;

FIG. 31 is a top view of the punch of FIG. 30 shown engaged with thelocking device;

FIG. 32 is a front section of the punch of FIG. 30 shown engaged withthe locking device;

FIG. 33 is a right side section of the punch of FIG. 30 shown engagedwith the locking device;

FIG. 34 is a perspective view of the punch and die of FIG. 30 after thepunch has acted on the locking device; and

FIG. 35 is a front elevational view of the die of FIG. 30 shown afterthe punch has acted on the locking device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An inventive cable tie 100 with a securely anchored metal locking deviceaccording to a first embodiment will be described with reference toFIGS. 4-15. As best shown in FIGS. 4-5, cable tie 100 includes a lockinghead 102 and a strap 104. Cable tie 100 can be made from variousmaterials as known in the art. Suitable materials include by way ofexample, nylon, polypropylene, and various fluoropolymers. Cable tie 100can be formed in various sizes and lengths to suit a particularapplication as also known in the art. Obviously, desired loop tensilestrength is one factor to decide when selecting sizing of the strap,locking head, locking device and other components.

While cable tie 100 is shown to have locking head 102 with a strapaccepting channel 122 parallel to a strap attachment axis S and a strapthat is bent at approximately 90° from strap attachment axis S, cabletie 100 is not limited to such a configuration and may take other forms.For example, the cable tie 100 may have a straight strap that continuesto extend substantially along axis S. Additionally, cable tie 100 mayhave a more conventional right angle locking head such as that shown inBernard '727, that has a strap accepting channel at a right angle tostrap attachment axis S.

Strap accepting channel 122 of cable tie head 102 receives a leading end112 of strap 104 during use. Strap accepting channel 122 includes astrap entry end 168 through which strap 104 is first inserted and astrap exit end 166. Leading end 112 is preferably tapered. Strap 104 maybe provided with a longitudinally extending central groove 110 on theinside surface and a longitudinally extending central slot on theoutside surface (unshown). Central groove 110 may taper at the end ofthe strap adjacent locking head 102 to form an increased width, such asby providing a V-groove 120 as best shown in FIGS. 4-5.

As better shown in FIGS. 6-8, locking head 102 also includes a lockingdevice receiving cavity 180. Locking device receiving cavity 180provides access to the anchoring region for metal locking device 136 forpartial embedding of metal locking device 136 in a mounting slot 130 oflocking head 102 to define a cantilever beam structure having a fixedend 134 and a free end 138 that extends into strap accepting cavity 122.Metal locking device receiving cavity 180 also allows for movement oflocking device 136 and includes a relief portion 182 (recessed wall) andprotruding wall portion 184. Relief 182 is formed in end wall 124 at alower part of receiving cavity 180 adjacent to the mounting slot 130.Mounting slot 130 also includes an outer support surface 164 and aninner support surface 162.

Metal locking device 136 is preferably formed from a corrosion resistantmetal, such as stainless steel as known in the art. While metal lockingdevice 136 may take a conventional straight form, it is preferably bentor formed so that free end 138 is at a predetermined angle relative tofixed end 134. It is also preferable for fixed end 134 to besubstantially parallel to the axis of strap accepting channel 122. Thisallows for easier insertion of locking device 136 into cavity 180. Italso allows for a lower profile cable tie head. In any case, free end138 extends into strap accepting channel 122 at an acute angle relativeto the axis of strap accepting channel 122 facing strap exit end 166.Moreover, according to the invention, metal locking device 136 isprovided with one or more bent protruding tangs 132 that project outwardfrom the surface of fixed end 134 and act to anchor the locking devicewithin support cavity 130 of locking head 102.

A first preferred embodiment of the metal locking device 136 is shown inFIGS. 10-13 and has two bent tangs 132, which are preferably formed onedge surfaces of fixed end 134 and are angled outward. Anotherembodiment of the metal locking device is shown in FIGS. 14-15 andincludes a single bent tang 132 projecting from an intermediate surfaceof the locking device 136.

Referring back to FIGS. 7-8, metal locking device 136 is shown beinginstalled through receiving cavity 180 and partially inserted intomounting slot 130. FIG. 9 shows the metal locking device 136 fullyinserted. As best shown in FIG. 8, when the metal locking device 136 isinstalled, relief 182 allows the locking device to be inserted withoutinterference with the locking device receiving cavity walls until themetal locking device 136 has been sufficiently inserted into themounting slot 130. This keeps the metal locking device straight duringinstallation. At such time of partial insertion, fixed end 134penetrates through an entrance of the mounting slot 130 while the atleast one bent protruding tang 132 is still located in receiving cavity180. That is, bent tang 132 is accommodated by the relief 182 so as toalign the metal locking device while not inhibiting insertion. Uponfurther insertion, the at least one bent tang 132 is forced through theentrance to mounting slot 130 as shown and the inner support surface 162becomes displaced (i.e., pushed to the right as shown in FIG. 8). Aftersufficient insertion, bent tang 132 becomes substantially within, andpreferably entirely within, mounting slot 130, as shown in FIG. 9. Dueto this configuration, two elements assist in retaining the metallocking device securely within the mounting slot 130. First, the urgedinner support surface 162 acts to bias the locking device 136 toward theouter support surface 164. That is, the inner support surface 162elastically relaxes in an attempt to return to its original position.Further, while the shape of the bent tang 132 allows for a rather lowresistance to insertion, due to the outwardly projecting jagged edges,tangs 132 tend to bite into the outer support surface 164 due to thebiasing from the inner support surface 162. Forces acting to remove thefree end of the strap in direction P, as shown in FIGS. 2 and 9, act tofurther urge the sharp jagged edge of bent tang 132 against the outersupport surface 164 effectively increasing the anchoring force providedby this structure. Forces acting to remove the metal locking device fromslot 130 in direction T, as shown in FIG. 9, are resisted by the bitingengagement of tang 132 against outer support surface 164.

Referring back to FIGS. 7-9, once fully inserted, cantilevered metallocking device 136 is supported at a fulcrum point defined by an upperedge 142 of an inner wall of cable head 102. Metal locking device 136has a free length defined from the fulcrum point to free end 138 thatallows free end 138 to extend into channel 122 by a distance tosufficiently engage a strap being threaded through strap acceptingchannel 122 and prevent withdrawal of the strap from the channel.

A second embodiment of the invention will be shown with reference toFIGS. 16-23. As better shown in FIGS. 16-18, cable tie head 102 includesa locking device receiving cavity 180 as in the first embodiment.Locking device receiving cavity 180 receives metal locking device 136and is provided to allow access for partial embedding of metal lockingdevice 136 in a mounting slot 160 of cable tie head 102. As in the firstembodiment, metal locking device receiving cavity 180 also allows formovement of locking device 136 and includes a relief portion 182(recessed wall) and protruding wall portion 184.

As with the locking device of the first embodiment, metal locking device136, of this second embodiment can be provided with one or more bentprotruding tangs 132 that project outward from the surface of fixed end134. These bent tangs may be the same as the exemplary bent tangs shownin FIGS. 10-15. Thus, while it is to be noted that this secondembodiment is being shown and described with the metal locking device136 as shown in FIGS. 14 and 15, neither the first or the secondembodiments are limited to the locking devices shown.

As can be seen in FIG. 17, an entrance slot 152 is formed in a wallportion 150 disposed at an interior wall of mounting slot 160. Entranceslot 152 is preferably less thick than locking device 136. As in thefirst embodiment, mounting slot 160 also includes an outer supportsurface 164 and an inner support surface 162. However, in the secondembodiment, the slot 160 is preformed and is designed with inner andouter support walls that are farther apart than the width of entranceslot 152 so as to define a receiving ledge 154 on a lower side of wallportion 150 between entrance 152 and outer surface 164. As best shown inFIG. 23, mounting slot 160 may include an opening that extends to theexterior of cable tie head 102.

Referring back to FIGS. 17-18, metal locking device 136 is shown beinginstalled through receiving cavity 180 and partially inserted intomounting slot 16O. FIGS. 19-20 show the metal locking device 136 fullyinserted. As best shown in FIG. 18, when the metal locking device 136 isbeing installed, relief 182 allows the locking device to be insertedwithout interference with the locking device receiving cavity wallsuntil the metal locking device 136 has been sufficiently inserted intothe slot 160. This keeps the metal locking device straight duringinstallation. At such time of partial insertion, fixed end 134penetrates through wall 150 via entrance slot 152 of the mounting slot160 while the at least one bent protruding tang 132 is still located inreceiving cavity 180 above wall portion 150. That is, bent tang 132 isaccommodated by the relief 182 so as to align the metal locking devicewhile not inhibiting insertion. Upon further insertion, the at least onebent tang 132 is forced through the wall 150 to mounting slot 160 asshown and the inner support surface 162 becomes displaced (i.e., pushedto the right). After sufficient insertion, bent tang 132 becomessubstantially within, and preferably entirely within, mounting slot 160,as shown in FIGS. 19-20. Due to this configuration, several elementsassist in retaining the metal locking device securely within themounting slot 160. First, the urged inner support surface 162 acts tobias the locking device 136 toward the outer support surface 164. Thatis, the inner support surface 162 elastically relaxes in an attempt toreturn to its original position. Further, while the shape of the benttang 132 allows for a rather low resistance to insertion, due to theoutwardly projecting jagged edges, tangs 132 tend to bite into the outersupport surface 164 due to the biasing from the inner support surface162. Forces acting to remove the metal locking device from slot 160 indirection T, as shown in FIG. 20, are resisted by the biting engagementof the sharp jagged edge of bent tang 132 against the outer supportsurface 164 and retaining ledge 154.

Additional views of the second embodiment are shown in FIGS. 21-23,which show mounting slot 160 including an opening that extends entirelythrough the cable head 102 and to an external surface. The opening maybe provided for manufacturing reasons and should be smaller than thelateral width of the locking device 136. The bent tangs 132 of the metallocking device can be formed by any known or subsequently developedmethod. However, two exemplary methods of forming bent tangs 132 for thepreferred first embodiment (FIGS. 10-13) are illustrated in FIGS. 24-35.In FIG. 24, metal locking device 136 is placed in a punching die 300 andis acted upon by a punching ram 350. As shown, fixed end 134 overhangsdie 300 by a predetermined distance corresponding to a desired locationof bent tangs 132. Upon pressing of ram 350 against die 300 with asuitable pressing force dependent upon the material and size of element136 selected, and subsequent opening of the die, metal locking devices136 can be formed with the desired bent tangs 132 as shown in FIG. 28.Bent tangs 132 are better shown in the close-up of FIG. 29. To make theillustrated exemplary bent tangs, a lower face of punching ram 350 isprovided with an inverted V-shaped tooling surface. However, this ismerely one example of a tang structure. Other suitable tang structuresare contemplated.

Once the bent tangs are formed, the metal locking device 136 is suitablyformed and bent into the angled shape so that the free end is angledrelative to the fixed end, such as by the method described in co-pendingU.S. patent application Ser. No. 09/858,049, now U.S. Pat. No.6,484,367, the subject matter of which is incorporated herein byreference in its entirety. Alternatively, the bent tangs may be formedafter the metal locking device has been bent in the angled shape.

An alternative embodiment further is provided with a support base 400,which supports the overhanging portion of metal locking device 136 thatextends beyond die 300 as shown in FIGS. 30-35. In this embodiment, thefixed end 134 is not free floating during punching but is insteadsupported by base 400. To allow for formation of the bent tangs 132,support base 400 is provided with a support surface 402 and two tangreceiving cavities 404. During punching, support surface 402 willsupport the overhanging section of metal locking device 136. However,the cavities 404 allow formation of the tangs 132.

With either of the above embodiments, a beneficial anchoring of thelocking device to the cable tie head can be achieved. The at least onetang provides additional resistance to metal locking device pullout toprevent failures of the cable ties, particularly during cable tiere-threading procedures after initial tensioning. The at least one tangalso reduces the required depth of the anchor over that of previoussystems that relied upon a straight locking device fixed end andfrictional fit. Alternatively, instead of a single punching ram, twopunching rams may be provided, with each forming one of the two benttangs 132. In such a case, each ram could have a working face angled atan acute angle to the face of the metal locking device.

While the systems of the invention have been described in conjunctionwith the specific embodiments outlined above, it is evident that manyalternatives, modifications and variations will be apparent to thoseskilled in the art. Accordingly, the exemplary embodiments are intendedto be illustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A method of forming a cable tie having astrengthened anchoring system, comprising the steps of: forming a cabletie having a strap including a first end and a free end and a lockinghead secured to the first end of the strap, the locking head defining astrap accepting channel in the head having a strap entry end and a strapexit end, the locking head further including a metal locking devicereceiving cavity adjacent to and open toward the strap exit end of thelocking head, the locking head further including a mounting slot havingan inner support wall and an outer support wall; forming a metal lockingdevice with a fixed end having at least one bent tang and a free end;initially mounting the metal locking device through the metal lockingdevice receiving cavity into the mounting slot by inserting the fixedend into the support cavity until the fixed end is urged against theinner support wall; and further inserting the metal locking device intothe mounting slot and causing the inner support surface to beresiliently deformed until the at least one bent tang is substantiallyreceived within the mounting slot, at which time the inner supportsurface urges at least an edge of the at least one bent tang against theouter support surface to securely anchor the metal locking device to themounting slot.
 2. The method of claim 1, wherein the at least one benttang is formed by punch pressing of the metal locking device.
 3. Themethod of claim 2, wherein the punch pressing forms a three-sided cut inthe metal locking device to form a single bent barb.
 4. The method ofclaim 2, wherein the punch pressing forms two bent tabs extendingoutward from side edges of the fixed end.
 5. The method of claim 4,wherein the punch pressing is achieved in a single blow from a press ramat an angle normal to the face of the metal locking device.
 6. Themethod of claim 1, wherein the step of forming a receiving cavity formsa receiving cavity wall with a relief sized to accommodate the at leastone bent tang and minimize interference during metal locking deviceinsertion.
 7. The method of claim 1, further comprising a step ofbending the free end of the metal locking device to be angled relativeto the fixed end.
 8. The method of claim 1, wherein the step of formingthe cable tie head forms the strap accepting channel and the mountingslot to be substantially parallel.